Migrate Mimir tracing to opentelemetry

[pracucci]

Is your feature request related to a problem? Please describe.

Mimir tracing is based on jaeger client and opentracing, which are deprecated.

Describe the solution you'd like

• Migrate to opentelemetry.
• Being consistent between Mimir, Loki and Tempo (hopefully sharing the same code)
  • Tempo introduced opentelemetry tracer support (optional) in http://github.com/grafana/tempo/pull/842
  • Loki hasn't introduced opentelemetry yet

Describe alternatives you've considered

Nothing else considered.

[bboreham]

• [Trace] Mimimum changes in dskit in order to migrate to opentelemetry dskit#385